|Title of Invention||
A PROCESS FOR PREPARATION OF A VISCOUS AND THIXOTROPIC ANAEROBIC ANAEROBIC ADHESHIVE COMPOSITION
|Abstract||A process for the preparation of a formulation useful as a viscous and thixotropic anaerobic adhesive composition A process for the preparation of a formulation useful as a viscous and thixotropic anaerobic adhesive composition by heating the monomer in glass vessel to 70 to 80°C under stirring, adding thickening agent while passing oxygen gas into the monomer to obtain clear viscous monomer liquid, adding imides in the range of 0.4 to 1% by wt of monomers, to this adding accelelator in the range of 0.2-1% by wt of monomers stabilizer in the range of 0.04 to 0.8% by wt of the monomers, initiators in the range of 2-10% by wt. of monomers, adding thickening agent in the range of 5-10 phm to obtain the adhesive composition.|
|Full Text||This invention relates to a process for the preparation of reformulation a viscous and thixotropic anaerobic adhesive composition. This invention particularly relates to highly viscous polymerisable compositions, the polymerisation of which is inhibited by the presence of air or oxygen and which polymerised spontaneously upon the substantial exclusion of air and free oxygen. Such compositions are generally known a s and are hereinafter referred to as Anaerobically Curable Compositions and are said to be "Capable of curing Anaerobically".
Anaerobic adhesive compositions because of their unique characteristics have found utility as polymerisable adhesives and sealants. The fact that these compositions generally are readily flowable low vicous liquids, however, as placed limitations on their area of use. In production line applications, it has been found necessary to apply the liquid immediately before assembly because of the tendency of liquid adhesive to flow, which migrates from one part to the surrounding areas. This can pose many problems especially in the assembly line where it may bond unnecessary parts and making the assembly unusable. Particularly, when used in large volume applications, where automatic parts handling and application equipments are used, the anaerobic composition can migrate to and penetrate into various moving parts of the equipment. Various attempts have been made to increase the viscosity to any desired level without sacrifying the performance of the adhesive. There are several patents available on the anaerobic adhesives.
1. Burnett, R.E., and Nordlander, B.W., U.S. Patent 2,628,178 (Feb.10,
2. Krieble, V. K., U.S. Patent 2,895,950 (July 21, 1959).
3. Krieble, V. K., U.S. Patent 3,041,322 (June 26,1962)
4. Krieble, R. H., U.S. Patent 3,043,820 (July 10,1962).
5. Krieble, R. H., Private Communication
6. Krieble, V. K., U.S. Patent 3,046,262 (July 24, 1962).
7. Krieble, V. K., U.S. Patent 3,218,305 (Nov. 16, 1965).
8. Gorman, J. W., and Toback, A. S., U.S. Patent 3,425,988 (Feb. 4,1969)
9. Toback, A. S., and Cass, W. E., U.S. Patent 3,625,930 (Dec 7, 1971)
But non of these patents have described the actual process of making this compositions and also most of them have low viscosity. There are several disadvantages with these low viscous anaerobic adhesives as they can migrate and penetrate into various other moving parts of the equipment and making the assembly unusable. Not only that these patents have described the anaerobic adhesives which cure in 30 to 60 minutes duration. In the present investigation highly viscous and thixotropic anaerobic adhesive compositions are made to over come the defects mentioned in the published patents Also an improved process of making these compositions ie., the sequence of addition of the each component has been mentioned which is most important in making these formulations, having good storage stability and extended a performance guarantees. The curing time has also been reduced to almost 15 to 40 minutes.
The principal novel feature of the compositions of the present invention is that the thickening agents such as polymethylmethacrylate, aluminium stearate hydrogenerated castor oil and chlorinated paraffin wax are used in the anaerobically cured adhesive compositions to increase the viscosity 1000 CPS and above Amorphous silica and finely dispersed polyethylene are also used for making the compositions thixotropic.
In view of the fact that thixotropy is obtained by the use of comparatively insoluble organic compounds which serve as thixotropic agents, the systems of this invention are easily prepared in the sense that extreme control over the amount of material added is not required. Since these thixotropic agents do not form highly structured systems and therefore, the thixotropic conditions are prevailed even after the substantial periods of storage time. When such attempts are made, some other problems are likely to crop up. The increase in viscosity may reduce the ability of the anaerobic adhesive compositions to penetrate into the interstices; between the closely fitted parts and also may increase the tendency of the anaerobic adhesive composition to be wiped out from the application site which has to be mated. In addition, the object of the present invention is also to reduce these defects by employing the soluble thickening agents such as high molecular polymethylmethacrylate (1,00,000 - 2,00,000) specially prepared by suspension polymerisation, hydrogenerated castor oil, aluminium stearate. and chlorinated paraffinwax. The most desirable monomers for the use in the thixotropic anaerobic adhesive formulations of this invension are
dimethacrylate esters such as tetraethyleneglycol dimethacrylate, triethyleneglycol dimethacrylate, polyethyleneglycol dimethacrylate.
The liquid thixotropic anaerobic compositions discussed herein" contained hydroperoxy polymerisation initiator capable of polymerising the diacrylate and dimethacrylate monomers in the substantial absence of oxygen. The hydroperoxides are highly superior and compositions containing them constitute highly preferred embodiments of this invention. Thus, hydroperoxide systems are the only ones which are highly suitable and therefore, achieve the results of commercial acceptance. The typical examples of such organic hydroperoxides used here are cumene hydroperoxide, t.butyl hydroperoxide, methyl ethyl ketone hydroperoxide etc. These hydroperoxide initiators used in the present formulations are in the range of 0.1% to 10% by weight of the combination. The levels above this, adversely affect the strength of the cured compositions due to the effect of dilution.
While the benefits of this invention are achievable in these anaerobic compositions, for faster curing, latent polymerisation accelators have to be incorporated into the formulations. The most common of these accelators suitable in the thixotropic compositions are_t.amines NN-dialkyl aryl amines such as NN-dimethyl paratoluidine. Though, certain other primary amines or secondary amines can be used as accelerators but care must be taken for the stability of the compositions. Other t.amines such as piperidene and
1,2,3,4 tetrahydroquinolene can also be used in these formulations, as mentioned in our copending Application No. 1089/Del/99.
Another highly useful accelator is organic sulphimide such as benzoic sulphimide (saccharin). The combination of benzoic sulphimide with NN-dimethyl paratoluidine is proved to be the most preferred ones in the anaerobic adhesive compositions. The most preferable amounts of NN-dimethyl paratoluidine used in the anaerobic adhesive compositions of this invention is in the range of 0.2 to 1 percent on the weight of the anaerobic monomer. The benzoic sulphimide accelator is used in the range of 0.4 to 1 percent by weight of anaerobic monomer. Though, in some cases, its percentage can be increased upto a level of 4%.
Other ingredients used in this present invention are the stabilisers such
as benzoquinones used in the range of 0.04 to0.08 percent on the weight of the
monomer so as to keep the thixotropic anaerobic compositions stable for more than one year.
Accordingly, the present invention provides a process for the preparation of a viscous and thixotropic anaerobic
adhesive composition which comprises heating the monomer in glass vessel
to 70 to 80°C under stirring, adding thickening agent in the range of 5-10 phm while passing oxygen
gas into the monomer to obtain clear viscous monomer liquid, adding imides
in the range of 0.4 to 1% by wt of monomers, to this adding accelelator in the
ange of 0.2-1% by wt of monomers stabilizer in the range of 0.04 to 0.08 by
wt of the monomers, initiators in the range of 2-10% by wt. of monomers,
to obtain the adhesive composition.
In an embodiment of the present invention the monomers used may be selected from diethyleneglycol dimethacrylate, triethyleneglycol dimethacrylate, tetraethylene glycol dimethacrylate, polytheleneglycol dimethacrylate and tri methylol propane trimethacrylate.
In an another embodiment of the invention the initiators used may be selected from cumene hydroperoxide, tertiary butylhydroperoxide, methylethylketone hydroperoxide.
In still another embodiment of the invention the imides used may be selected from orthobenzoic acid sulphimide (saccharin).
Still another embodiment of the invention the accelerators used may be selected from N - N dimethyl para toluidene, triethyl amine, tetra hydroquinolene, di-methyl aniline.
In an another embodiment of the present invention the stabilisers used may be selected from benzoquinone, naphthoquinones, anthraquinone.
In still another embodiment of the present invention the viscous and thixotropic thickening agents used may be selected from polymethyl methacrylate, polystyrene, chlorinated paraffin wax, aluminium stearate, hydrogenated castoroil, amorphous silica and micronised polyethylene.
Following examples are given to demonstrate the preparation and use of compositions within the scope of invention disclosed herein. The
examples are not intended to be limitations upon the scope of the invention. All weights in the following examples are on weight basis.
EXAMPLE – 1
The monomer tetraethyleneglycol dimethacrylate (TETEGDMA) was heated in a glass vessel to 70-80°C under stirring and to which the thickening agent was added gradually while passing oxygen gas into the monomer. After obtaining a clear viscous monomer liquid (100 parts), saccharin
dimethyl paratoluidine, 1,4 benzoquinone and cumene hydroperoxide were added in sequence at 30°C in quantities as shown in the following table:
All these formulations were then measured for their viscosity using Brookfield viscometer. These formulations were also tested for their stability by heating them at 82°C for 3Omin. If there is no apparent increase in the viscosity at the end of 30 min.it is understood that these formulations are all stable for more than one year at 30°C. All these anaerobic adhesive
compositions were tested on standard 3/8" bolt and a mating nut by placing several drops of the adhesive on the threaded area to determine their cure characteristics. The torque strength of the mated assemblies was tested as per MIL-S-22473D specifications after 24 h of cure. The torque strengths are given in the following table.
EXAMPLE - 2
Thixotropic anaerobic adhesive compositions were prepared by dispersing thixotropic agents such as amorphous silica and micronised polyethylene into the anaerobic adhesive compositions using sigma mixer. The anaerobic monomer tetraethyleneglycol dimethacrylate (100 parts) was mixed with saccharin (4 parts), dimethyl paratoluidine (1 part) and 1,4 benzoquinone (0.1 part). To this composition, amorphous silica (10 parts) was added and thoroughly mixed. To this cumene hydroperoxide (2 parts) added. This thixotropic anaerobic adhesive composition had
viscosity 12000 CPS as determined by the Brookfield viscometer. This composition had stability of over 40 min at 82°C. The initial set time was 60 min. When this composition was used on threaded assemblies of 3/8" nuts and bolts gave a prevailing torque of 1.20 kg.M.
EXAMPLE - 3
The thixotropic anaerobic composition was prepared by dispersing polyethylene powder (10 parts) in polyethylene glycol dimethacrylate (100 parts) in presence of oxygen. In this viscous anaerobic monomer saccharin (4 parts) dimethyl p.toluidine (1 part) and 1,4 benzoquinone (0.01 part)were added and cumene hydroperoxide (2 parts) was mixed. This thixotropic anaerobic adhesive composition had viscosity 15000 CPS as determined by the Brookfeild viscometer. This composition was stable for over 40 min. at 82°C. The initial set time was 60 min when this composition was used on threaded assemblies of 3/8" nuts and bolts and gave prevailing troque of 1.38 kg/M. The same composition when polyethylene powder was not used, the composition had viscosity of only 20 CPS and gave the prevailing torque of 0.69 kg/M.
The main advantages of this invention are -
1) These anaerobic (sealant) adhesive compositions could be made with
different viscosities which are commercially acceptable.
2) These thixotropic anaerobic (sealant) adhesive compositions cure in 30 -
60 min. between the threaded assemblies where there is an exclusion of
3) The thickening agents useful to increase the viscosity are polymethyl
methacrylate, polystyrene chlorinated paraffin wax, aluminium stearate,
hydrogenated castoroil, amorphous silica and micronised polyethylene
are used effectively.
4) These anaerobic compositions have 6 components i.e., (a)monomers (dimethacrylate) (b)initiators (hydroperoxides) (c)imides (saccharin) (d)accelators (amines) (e)stabilisers (quinones) and (f)thickenning agents.
By varying these components, the adhesive (sealant) compositions of desired /viscosity could be prepared to meet the demands of the Engineering Industry with specific cure times and torque strengths.
A process for the preparation ofdelete a viscous and thixotropic
naerobic adhesive composition which comprises heating the
agent in the range of 5-10 phm while passing oxygen gas into the monomer to obtain clear viscous
monomer liquid, adding imides in the range of 0.4 to 1% by wt of
monomers, to this adding accelelator in the range of 0.2-1% by wt of monomers stabilizer in the range of 0.08 by wt of the monomers,
not haveing support initiators in the range of 2-10% by wt. of monomers, in to obtain the adhesive composition
2. A process as claimed in claim (1), wherein the monomers used
is selected from dimethacrylate, triethyleneglycol dimethacrylate, tetra
ethylene glycol dimethacrylate, polytheleneglycol dimethacrylate and tri
methylol propane tri meth aery late.
3. A process as claimed in claims (1) and (2) wherein thejnitiators used are
selected from cumene hydroperoxide, tertiary butyl hydroperoxide, methyl
ethyl ketone hydroperoxide
4. A process as claimed in claims (1) to (3) wherein imides used is orthobenzoic acid sulphimide (saccharin)
5. A process as claimed in claims (1) to (4) wherein the accelerators used are selected from N - N dimethyl para toluidene.triethyl amine, 1, 2, 3, 4 tetra hydroquinolene, di-methyl aniline
6. A process as claimed in claims (1) to (5), wherein stabilisers are used
selected from 1,4 benzoquinone, naphthoquinones, anthraquinone not supported by descripition
7. A process as claimed in claims (1) to (6) in the viscous thixotropic
thickening agent selected from polymethyl methacrylate, polystyrene,
chlorinated paraffin wax, aluminium stearate, hydrogenated castoroil
amorphous silica and micronised polyethylene.
|Indian Patent Application Number||283/DEL/1999|
|PG Journal Number||12/2008|
|Date of Filing||19-Feb-1999|
|Name of Patentee||COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH|
|Applicant Address||RAFI MARG, NEW DELHI-110001, INDIA.|
|PCT International Classification Number||C09J 3/14|
|PCT International Application Number||N/A|
|PCT International Filing date|